This invention relates generally to tuned exhaust systems for two-cycle internal combustion engines and in particular to tuned exhaust systems in which exhaust pulses are reflected and propagated so as to provide desirable pressures at the engine exhaust ports and thereby improve engine efficiency.
It is known to improve the power and brake specific fuel consumption of a two-cycle internal combustion engine, having an even number of cylinders, through use of a tuned exhaust system operable to reduce exhaust port pressure during the scavenging portion of each cylinder's power stroke and to increase exhaust port pressure immediately following transfer port closure during each cylinder's compression stroke. Although effective, tuned exhaust systems for two-cycle engines have been relatively expensive and complex in construction. Additionally, such known tuned exhaust systems are typically tuned to a single engine speed and thus do not function to provide improved engine performance at both midrange and high engine speeds.
Tuned exhaust systems for two-cycle engines are shown, for example, in the following U.S. Pat. Nos.:
______________________________________ Nowak, et al. 4,186,819 Feb. 5, 1980 Brooks, et al. 3,875,744 Apr. 8, 1975 Boerma 3,695,238 Oct. 3, 1972 Miller, et al. 3,692,006 Sept. 19, 1972 ______________________________________
Attention is also directed to the following U.S. and foreign patent documents:
______________________________________ Date et al. 4,197,704 Apr. 15, 1980 Schmidt 3,882,681 May 13, 1975 Christensen 3,605,940 Sept 20, 1971 Knox, Jr. 3,516,247 June 23, 1970 Biesecker 3,453,824 July 8, 1969 Wilson 2,306,580 Dec. 29, 1942 (France) 886,556 Oct. 19, 1943 (Italy) 505,515 Dec. 17, 1954 (Germany) 996,932 Sept 19, 1957 (Germany) 760,421 May 4, 1953 ______________________________________